As first reported in the Kurier newspaper, and confirmed to APA by Austrian air traffic control spokesman Markus Pohanka on Saturday, some of the civilian aircraft were no longer visible on controller's displays for nearly half an hour.
Pohanka emphasized that "Position data were replaced by radio contact", and that no travelers were in danger at any time due to the failure.
In addition, there is for "every conceivable situation in air traffic control a corresponding backup method," Pohanka said.
At the same time, there were similar failures in air traffic control experienced by Hungary, Germany, Slovakia and the Czech Republic. Technical checks confirmed that there were no problems with Austria Control's systems, leading them to conclude that the problems may be linked to NATO exercises occurring in Hungary at the time of the failure.
The Federal Army, which oversees the military airspace,was not affected by the failure.
"We have both a primary and a secondary radar," said Colonel Michael Bauer. The primary radar can locate flying objects themselves.
The Austro Control, however, works with secondary radar. This is dependent on a transponder signal from the aircraft, which provides additional information to identify the aircraft. If this transponder signal is absent, the aircraft will not be noticed by a secondary radar.
According to the Kurier newspaper, a NATO exercise for electronic warfare was being conducted in Hungary at the time, which included the blocking of aircraft transponders on the practice schedule. Problems with radar systems were also reported from several NATO member countries.
Also affected was the Karlsruhe control center of the German Air Traffic Control (DFS), who monitor a significant part of German airspace.